Field of the Invention
The present invention relates to bispecific molecules that are capable of localizing an immune effector cell that expresses an activating receptor to a virally infected cell, so as to thereby facilitate the killing of the virally infected cell. In a preferred embodiment, such localization is accomplished using bispecific molecules that are immunoreactive both to an activating receptor of an immune effector cell and to an epitope of an antigen expressed by a cell infected with a virus. The present invention additionally concerns the use of such bispecific molecules in the treatment of latent viral infections, persistent viral infections and inactive viral infections, and the use of such bispecific molecules in methods to kill cells containing a viral genome or cell expressing a viral protein. The invention particularly concerns bispecific molecules that bind to (1) an epitope of an activating receptor of an immune effector cell and (2) an epitope of an antigen expressed by a cell infected with a virus wherein the antigen is detectably present on the cell infected by the virus at a level that is greater than the level at which the antigen is detected on the virus by the bispecific molecules and to such bispecific molecules that are capable of mediating, and more preferably enhancing, the activation and targeting of the immune effector cells to the cell infected by the virus such that the activated immune effector cells kill the cell infected by the virus.
Description of Related Art
I. Viral Infectious Disease
The last few decades have seen a revival of interest in the therapeutic potential of antibodies, and antibodies have become one of the leading classes of biotechnology-derived drugs (Chan, C. E. et al. (2009) “The Use Of Antibodies In The Treatment Of Infectious Diseases,” Singapore Med. J. 50(7):663-666). Nearly 200 antibody-based drugs have been approved for use or are under development.
Such drugs hold particular promise for the treatment of infectious diseases, and most significantly, for the treatment of viral infectious diseases. Many pathogens have demonstrated a marked ability to gain resistance to conventional antimicrobial drugs (e.g., methicillin-resistant Staphylococcus aureus, extreme drug-resistant Mycobacterium tuberculosis and antimicrobial resistant Plasmodium falciparum). Other pathogens, such as HIV, influenza virus, etc. are presently not satisfactorily treatable using traditional drugs (see, Beigel, J. et al. (2008) “Current And Future Antiviral Therapy Of Severe Seasonal And Avian Influenza,” Antiviral Res. 78(1):91-102). Moreover, such drugs exhibit significant side effects. In contrast to traditional drugs, antibodies have two properties that make them highly attractive as therapeutic agents. First, since antibodies are endogenous proteins native to the body, they exhibit low toxicity. Second, they exhibit high specificity, which enables the directed targeting of infected cells.
However, present immunotherapy has certain drawbacks (Chan, C. E. et al. (2009) “The Use Of Antibodies In The Treatment Of Infectious Diseases,” Singapore Med. J. 50(7):663-666). The clearance of a viral infection is usually associated with T cell-mediated adaptive immunity. CD8+ T cells act by killing virally-infected cells, thus preventing viral replication and reducing the viral load. In addition, antibodies can promote the killing of infected cells expressing viral proteins on their surface through the activation of natural killer (NK) cells that mediate ADCC, in addition to their viral neutralization properties. Although antibodies have been shown to be able to neutralize many viral pathogens in vitro, the extent to which antibody-mediated immunity can achieve viral clearance in vivo is unclear. Thus, neutralizing therapeutic antibodies are typically administered not to mediate clearance, but rather to suppress viral replication and viremia and give the host immune system time to develop an effective response for viral clearance. In this regard, studies have shown that the capacity of antibodies to reduce viral load correlated with the persistence of the administered antibody in serum, and that viral antigen levels eventually recovered once antibody levels in the serum had declined following the cessation of therapy (Galun, E. et al. (2002) “Clinical Evaluation (Phase I) Of A Combination Of Two Human Monoclonal Antibodies To HBV: Safety And Antiviral Properties,” Hepatology 35:673-679; Heijtink, R. A. et al. (2001) “Administration Of A Human Monoclonal Antibody (TUVIRUMAB) To Chronic Hepatitis B Patients Pre-Treated With Lamivudine: Monitoring Of Serum TUVIRUMAB In Immune Complexes,” J. Med. Virol. 64:427-434). Additionally, studies with HIV have shown that the regular administration of therapeutic antibodies may lead to the development of escape mutants (Chan, C. E. et al. (2009) “The Use Of Antibodies In The Treatment Of Infectious Diseases,” Singapore Med. J. 50(7):663-666). In one study, a combination of three broadly neutralizing HIV antibodies administered over a period of 12 weeks succeeded in delaying viral rebound after the cessation of antiviral treatment, relative to controls. However, viral levels eventually recovered despite the continued administration of all three antibodies, with increased resistance to one of the three administered antibodies (Trkola, A. et al. (2005) “Delay Of HIV-1 Rebound After Cessation Of Antiretroviral Therapy Through Passive Transfer Of Human Neutralizing Antibodies,” Nat. Med. 11:615-622).
II. Immune System Activation
CD4+ T-lymphocytes are the essential organizers of most mammalian immune and autoimmune responses (Dong, C. et al. (2003) “Immune Regulation by Novel Costimulatory Molecules,” Immunolog. Res. 28(1):39-48). The activation of CD4+ helper T-cells has been found to be mediated through co-stimulatory interactions between Antigen Presenting Cells and naive CD4+T-lymphocytes. Two interactions are required (Viglietta, V. et al. (2007) “Modulating Co-Stimulation,” Neurotherapeutics 4:666-675; Korman, A. J. et al. (2007) “Checkpoint Blockade in Cancer Immunotherapy,” Adv. Immunol. 90:297-339). In the first interaction, an Antigen Presenting Cell must display the relevant target antigen bound to the cell's major histocompatibility complex so that it can bind to the T-cell Receptor (“TCR”) of a naive CD4+T-lymphocyte. In the second interaction, a ligand of the Antigen Presenting Cell must bind to a CD28 receptor of the CD4+T-lymphocyte (Dong, C. et al. (2003) “Immune Regulation by Novel Costimulatory Molecules,” Immunolog. Res. 28(1):39-48; Lindley, P. S. et al. (2009) “The Clinical Utility Of Inhibiting CD28-Mediated Costimulation,” Immunol. Rev. 229:307-321). CD4+ helper T-cells experiencing both stimulatory signals are then capable of responding to cytokines (such as Interleukin-2 and Interleukin-12) to develop into Th1 cells. Such cells produce interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α), which mediate inflammatory responses to target cells expressing the target antigen. B-cell activation and proliferation also occurs, resulting in antibody production specific for the target antigen (Bernard, A. et al. (2005) “T and B Cell Cooperation: A Dance of Life and Death,” Transplantation 79:S8-S11). In the absence of both co-stimulatory signals during TCR engagement, T cells enter a functionally unresponsive state, referred to as clonal anergy (Khawli, L. A. et al. (2008) “Cytokine, Chemokine, and Co-Stimulatory Fusion Proteins for the Immunotherapy of Solid Tumors,” Exper. Pharmacol. 181:291-328). In pathologic states, Th1 cells are the key players of various organ-specific autoimmune diseases, such as type I diabetes, rheumatoid arthritis, and multiple sclerosis (Dong, C. et al. (2003) “Immune Regulation by Novel Costimulatory Molecules,” Immunolog. Res. 28(1):39-48).
III. Therapeutic Antibodies
In addition to their known uses in diagnostics, antibodies have been shown to be useful as therapeutic agents. For example, immunotherapy, or the use of antibodies for therapeutic purposes, has been used in recent years to treat infectious disease. Passive immunotherapy involves the use of monoclonal antibodies to treat infection (see for example, Ian Gust, A. O. (Epub 2012 Feb. 21) “Role Of Passive Immunotherapies In Managing Infectious Outbreaks,” Biologicals 40(3):196-199; Wang, D. et al. (2011) “Palivizumab For Immunoprophylaxis Of Respiratory Syncytial Virus (RSV) Bronchiolitis In High-Risk Infants And Young Children: A Systematic Review And Additional Economic Modelling Of Subgroup Analyses,” Health Technol. Assess. 15(5):iii-iv, 1-124; Rosenberg, H. F. et al. (2012) “Inflammatory Responses To Respiratory Syncytial Virus (RSV) Infection And The Development Of Immunomodulatory Pharmacotherapeutics,” Curr. Med. Chem. 19(10):1424-1431). These antibodies can have inherent therapeutic biological activity both by direct binding to the infectious agents (e.g., viruses, bacteria, fungi, etc.) and by their ability to bind to host cells that have been infected with such agents and which have expressed agent-specific antigens on their cell surfaces. These agents can be administered alone or in conjunction with other anti-infective agents (e.g., antibiotics, anti-inflammatory agents, anti-pyretic agents, etc.). Palivizumab, approved for treatment of respiratory syncytial virus (RSV) bronchiolitis, and tefibazumab (in clinical trials for the treatment of S. aureus infections) are examples of such therapeutics. Alternatively, antibodies can be used to make antibody conjugates in which the antibody is linked to a toxic agent and directs that agent to the tumor by specifically binding to the tumor. Gemtuzumab ozogamicin is an example of an approved antibody conjugate used for the treatment of leukemia in human patients.
Monoclonal antibodies that bind to virally-infected cells and have potential uses for diagnosis and therapy have been disclosed (see, for example, U.S. Pat. No. 8,313,746; U.S. Pat. No. 7,507,797; US 2012/0283438; US 2012/0128669; US 2012/0093834; US 2011/0319871; US 2011/0212076; US 2011/0076268; US 2011/0033389; US 2010/0040635; US 2010/0040601; US 2009/0162353; EP 1670826; WO 2011/085289; Oleksiewicz, M. B. et al. (Epub 2012 Jun. 13) “Anti-Bacterial Monoclonal Antibodies: Back To The Future?” Arch. Biochem. Biophys. 526(2):124-131; Huang, J. X. et al. (Epub 2012 Jun. 4) “Development Of Anti-Infectives Using Phage Display: Biological Agents Against Bacteria, Viruses, And Parasites,” Antimicrob. Agents Chemother. 56(9):4569-4582; Ian Gust, A. O. (Epub 2012 Feb. 21) “Role Of Passive Immunotherapies In Managing Infectious Outbreaks,” Biologicals 40(3): 196-199; Geevarghese, B. et al. (Epub 2012 Feb. 3) “Antibodies For Prevention And Treatment Of Respiratory Syncytial Virus Infections In Children,” Antivir. Ther. 17(1 Pt B):201-211; Rosenberg, H. F. et al. (2012) “Inflammatory Responses To Respiratory Syncytial Virus (RSV) Infection And The Development Of Immunomodulatory Pharmacotherapeutics,” Curr. Med. Chem. 19(10):1424-1431; Nossal, G. J. (2011) “Vaccines Of The Future,” Vaccine 29 Suppl 4:D111-115; Froude, J. W. et al. (2011) “Antibodies For Biodefense,” MAbs 3(6):517-527; Ter Meulen, J. (2011) “Monoclonal Antibodies In Infectious Diseases: Clinical Pipeline In 2011,” Infect. Dis. Clin. North Am. 25(4):789-802; Yamada, T. (2011) “Therapeutic Monoclonal Antibodies,” Keio J. Med. 60(2):37-46; Berry, J. D. et al. (2011) “Antibodies In Infectious Diseases: Polyclonals, Monoclonals And Niche Biotechnology,” Nature Biotechnol. 28(5):489-501; Whaley, K. J. et al. (2011) “Emerging Antibody Products And Nicotiana Manufacturing,” Hum. Vaccin. 7(3):349-356; Beasley, D. W. (2011) “Vaccines And Immunotherapeutics For The Prevention And Treatment Of Infections With West Nile Virus,” Immunotherapy 3(2):269-285; Wang, D. et al. (2011) “Palivizumab For Immunoprophylaxis Of Respiratory Syncytial Virus (RSV) Bronchiolitis In High-Risk Infants And Young Children: A Systematic Review And Additional Economic Modelling Of Subgroup Analyses,” Health Technol. Assess. 15(5):iii-iv, 1-124; Li, L. et al. (2010) “Immunotherapy For Prion Diseases: Opportunities And Obstacles,” Immunotherapy 2(2):269-282; Niebecker, R. et al. (2010) “Safety Of Therapeutic Monoclonal Antibodies,” Curr. Drug. Saf. 5(4):275-286; Hansel, T. T. et al. (2010) “The Safety And Side Effects Of Monoclonal Antibodies,” Nat. Rev. Drug Discov. 9(4):325-338; Chan, C. E. et al. (2009) “The Use Of Antibodies In The Treatment Of Infectious Diseases,” Singapore Med. J. 50(7):663-673; Beigel, J. et al. (2008) “Current And Future Antiviral Therapy Of Severe Seasonal And Avian Influenza,” Antiviral Res. 78(1):91-102; Huber, M. et al. (2008) “Antibodies For HIV Treatment And Prevention: Window Of Opportunity?” Curr. Top. Microbiol. Immunol. 317:39-66; ter Meulen, J. (2007) “Monoclonal Antibodies For Prophylaxis And Therapy Of Infectious Diseases,” Expert Opin. Emerg. Drugs. 12(4):525-540).
An ideal therapeutic and/or diagnostic antibody would be specific for an antigen present on infected cells, but absent or present only at low levels on any normal tissue. The discovery, characterization, and isolation of a novel antibody capable of binding to an antigen present on infected cells that is specifically associated with an infectious disease, and particularly a viral disease, would be useful in many ways. First, the antibody would have biological activity against such cells and be able to recruit the immune system's response to thereby treat the disease. The antibody could be administered as a therapeutic alone or in combination with current treatments or used to prepare immunoconjugates linked to toxic agents. An antibody with the same specificity but with low or no biological activity when administered alone could also be useful in that an antibody could be used to prepare an immunoconjugate with a radioisotope, a toxin, or a chemotherapeutic agent or liposome containing a chemotherapeutic agent, with the conjugated form being biologically active by virtue of the antibody directing the toxin to the antigen-containing cells.
One aspect desirable for an ideal therapeutic and/or diagnostic antibody would be the discovery and characterization of novel antibodies capable of mediating, and particularly of enhancing the activation of the immune system against infected cells (and especially against virally infected cells) that are associated with any of a variety of viral diseases.
Despite all prior advances, a need remains for improved compositions capable of binding to cells infected with a virus and of facilitating or mediating an immune response against the virally-infected cells. In addition, a need remains for improved compositions capable of detecting such virally-infected cells. It is an object of this invention to identify such compositions. It is another object to provide novel compounds for use in the detection of antigens expressed on the surface of virally-infected cells.
As described in detail below, the present invention relates to bispecific molecules that bind to 1) an epitope of an activating receptor of an immune effector cell and 2) an epitope of an antigen expressed by a cell infected with a virus and that such bispecific molecules are capable of mediating, and more preferably enhancing, the activation and targeting of the immune effector cells to the virally-infected cells expressing the epitope such that the activated immune effector cells kill the virally-infected cells.